[libvirt] [Qemu-devel] live snapshot wiki updated

Jes Sorensen Jes.Sorensen at redhat.com
Thu Jul 21 08:07:57 UTC 2011

On 07/20/11 21:51, Blue Swirl wrote:
>> And the snapshot_blkdev monitor command is a case where qemu needs to create
>> > a new qcow2 image on the fly, while referencing the name of an existing
>> > file.  What backing name do you put in the new qcow2 file unless you already
>> > have a name association for all fds already open for the existing backing
>> > file?
> For backing file with original name of "/path/in/storage", QEMU could
> present the fd and the backin path by requesting something like
> "fd:12,/path/in/storage". The next file in chain "/path2/file" would
> be "fd:12,fd:34,/path2/file". Or if possible, -fd 12 -backing
> /path/in/storage with spaces and funny characters escaped etc.

Rather than trying to do this by mangling files on the disk, I would
suggest we allow registering a call-back open function, which calls back
into libvirt and requests it to open a given file. It can then do all
it's security foo to decide whether or not to allow the file to be open.

This is relatively clean and avoids the mess of relying on outside
processes messing about in the images.


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